ajor
M
e
h
t
e
r
A
t
a
Wh
2
s
e
s
u
a
C
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atio
of Desertific
relationship with development pressure on land by human
activities which are one of the principal causes of
desertification. The table below shows the population in
drylands by each continent and as a percentage of the global
population of the continent. It reveals a high ratio especially in
Africa and Asia.
There is a vicious circle by which when many people live in
the dryland areas, they put pressure on vulnerable land by their
agricultural practices and through their daily activities, and as a
result, they cause further land degradation.
‘Climatic variations’ and ‘Human activities’ can be regarded as
the two main causes of desertification.
Climatic variations: Climate change, drought, moisture loss on a
global level
Human activities: These include overgrazing, deforestation and
removal of the natural vegetation cover（by taking too much fuel
wood）, agricultural activities in the vulnerable ecosystems of
arid and semi-arid areas, which are thus strained beyond their
capacity. These activities are triggered by population growth, the
impact of the market economy, and poverty.
Population levels of the vulnerable drylands have a close
▼ Main Causes of Soil Degradation by Region in Susceptible Drylands and Other Areas
Degraded Land Area in the Dryland: 1,035.2 million ha
0.9%
0.3%
18.4%
41.5%
7.7
%
11.4%
Europe
99.4
million ha
34.8%
North
America
79.5
32.1%
million ha
39.1%
Asia
52.1%
370.3
26.1%
5.4
%
million ha
11.5%
30.1%
16.9%
14.7%
79.1
million ha
4.8%
319.4
19.5%
40.7%
5.5
Africa
%
57.8%
million ha
33.1%
South
America
※
Overgrazing
Australia
87.5
Deforestation
million ha
Agricultural activities
5.8%
Source: WORLD
ATLAS OF
DESERTIFICATION
SECOND EDITION
（UNEP, 1997）
Overexploitation of vegetation
for domestic use
89.7%
Bio-industrial activities
▼ Population of the World’s Susceptible Drylands
（1,000 people）
Hyper-arid areas
■＝ % of total population of the respective continent
3 Dryland subtypes
Dry subhumid areas
Total
Africa
58,175
9%
41,366
6%
117,573
18%
109,038
16%
40%
Asia
29,506
1%
161,556
5%
500,695
15%
657,899
19%
39%
0
0%
275
1%
1,352
5%
5,318
19%
25%
Australia ※
Europe
Arid areas
Semiarid areas
0
0%
628
＜1%
28,811
5%
115,146
21%
26%
South America
3,877
1%
6,330
2%
46,851
16%
33,777
12%
30%
North America
508
＜1%
12,750
3%
53,900
13%
24,342
6%
22%
※Includes New Zealand and neighboring islands
Source: Aridity zones and dryland populations: an assessment of population levels in the world’s drylands with
particular reference to Africa（UNDP/UNSO, 1997）